There has been conventionally known a power generation device in which a pulley for an axle is provided at the axle of non-drive wheels of a vehicle as a rotation shaft, a pulley for a power generator is provided at a rotation shaft of the power generator provided in the vehicle, a belt is laid on the pulley for an axle and the pulley for a power generator, and electric power is generated by rotating the rotation shaft of the power generator with rotation of the non-drive wheel (refer to Patent Literature 1, for example).